Summary: The imbalance between nitrogen (N) and phosphorus (P) deposition may shift temperate ecosystems from N‐ to P‐limitation. However, it is unclear how the imbalanced N : P input affects the strategies of plants to acquire P and, therefore, the growth of plants and the competition among species. We conducted a 4‐yr N‐addition experiment in young and mature larch (Larix principis‐rupprechtii) stands. Plant growth and P acquisition strategies were assessed for larch and understorey vegetation. N addition stimulated the aboveground productivity of understorey vegetation in the young stand and larch in the mature stand, with other species unaffected. The competitive advantages of understorey vegetation in the young stand and larch in the mature stand were associated with their high stoichiometric homoeostasis. To maintain the N : P homoeostasis of these species, an increase in phosphatase activity but not P resorption efficiency increased the supply of P. Additionally, N addition accelerated P mineralization by decreasing the fungal‐to‐bacterial ratios and improved uptake of soil P by increasing the arbuscular mycorrhizas‐to‐ectomycorrhizas ratios. Our results suggest that plants with high stoichiometric homoeostasis could better cope with N deposition‐induced P‐deficiency. Although P resorption efficiency showed little plasticity in response, plants activated a variety of P‐acquisition pathways to alleviate the P‐deficiency caused by N deposition.

The intensive use of synthetic nitrogen fertilizers over the last century has both increased agricultural productivity and modified biogeochemical cycles in terrestrial ecosystems, causing severe negative environmental impacts. Tea (Camellia sinensis L.) plantations usually receive high levels of synthetic fertilizers, which strongly affect plant and soil properties. However, there is no quantitative study to assess how synthetic N additions affect soil chemistry and the production and quality of tea shoots. Here, we conducted a comprehensive meta-analysis to evaluate the effects of experimental synthetic N fertilizers. Our main findings are (1) N additions in tea plantations acidify soils (− 0.41 pH unit in average) and produce soil nutrient imbalance. Soil acidification commonly exacerbates the accumulations of toxic aluminum ions. (2) Synthetic N fertilizer additions may strongly increase tea production by almost 70% but alter tea shoot quality by increasing the concentrations of free amino acids (+ 16%), caffeine (+ 14%), and water extracts (+ 5%) while decreasing those of soluble sugars (− 8%) in the tea shoots. The responses of soil chemistry, tea production, and quality to N additions can vary among experimental conditions, tea tree species, and N fertilizer forms. Because there is statistical limitation in this meta-analysis, our findings recommend performing additional field studies to explore the potential mechanisms of nutrient cycling and ecosystem functioning under synthetic N additions. The development of a sustainable N management strategy in tea plantations is also urgently needed to enhance N use efficiency and reduce environmental risks.